1. Field of the Invention
The present invention concerns a long-life pump unit, which can be used for a number of types of withdrawals with a view to analyses. It is more particularly, but not exclusively, applicable to pipetting, dilution, rinsing and/or distribution of samples of liquid substances.
In general, one knows that a number of devices have already been proposed making it possible to perform pipetting and rinsing cycles, in particular within an analysis device.
2. Description of the Prior Art
These devices typically involve the use of a pumping module comprising a body provided with a working chamber, for example cylindrical, and a piston which can be in the form of a plunger which engages leaktightly in the working chamber. Actuation the piston is then done by a linear actuator comprising a rotating electric motor, for example of the step-by-step type, and a member converting the rectilinear movement into a rectilinear translational movement.
It has been seen that the pumping devices of this type currently produced have a certain number of drawbacks:
First of all, the conversion system which is used significantly increases the complexity of the device assembly as well as its cost.
Moreover, one encounters alignment problems between the linear movement actuation member and the piston: the alignment defects at this level lead to creating, on the seal which procures the leaktightness between the piston and the body of the pumping module, transverse stresses and, as a result, areas where abnormally high friction is produced which leads to premature wear of the seal. This is a relatively important drawback which increases maintenance costs and which, very often, reduces the life of the pumps.
Moreover, one drawback of the existing pump devices resides in the absence of modular nature and, in particular, of the possibility of quick interchangeability of the pumping module and the actuator.